\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{patterns}
\begin{document}
\footnotesize
  \begin{tikzpicture}[>=stealth]
    \foreach \x in{-0.8,-0.7,0.7,0.8} {\draw[thick](-2,\x)--(2,\x);}
    \foreach \x in{1.2,-1.2} 
      {
        \draw[thick](\x+0.05,-0.7)rectangle(\x-0.05,0.7);
        \filldraw[thick,fill=white](\x+0.2,-0.45)rectangle(\x-0.2,0.45);
        \draw[thin](\x,0.25)--(\x,-0.25);
      }
    \draw[thin,<->](-1.2,0)--(1.2,0)node[midway,above]{$s$};
    \draw[thin](-2,-0.9)--++(0,0.8)--++(30:0.1)--++(150:0.2)--++(30:0.1)--++(0,0.8);
    \draw[thin](2,-0.9)--++(0,0.8)--++(30:0.1)--++(150:0.2)--++(30:0.1)--++(0,0.8);
  \end{tikzpicture}
\end{document}